The present invention relates to a scanning electron microscope, for example, a scanning electron microscope which is designed in such a way that a condensed probe beam is applied to a surface of a sample held by sample holding means, and the secondary electrons emitted from the sample are collected through an electron optical system to detect the spin polarization of each of the secondary electrons, and more particularly to a scanning electron microscope which is suitable for the case where the orbits of the secondary electron are readily influenced due to the floating magnetic field and the like working on the position where the sample is mounted.
Heretofore, in a scanning electron microscope and the like, for the purpose of reducing the influence of the working floating magnetic field upon a probe beam and/or the orbits of the secondary electrons, a magnetic shield which is made of a material having high magnetic permeability is arranged on an internal surface of a sample chamber, or alternatively the sample chamber itself is made of a material having high magnetic permeability. For example, the Mott detector which is introduced in FIG. 1 of an article entitled "SPIN POLARIZATION DUE TO LOW-ENERGY ELECTRON DIFFRACTION AT THE W(001) SURFACE" by Koike et al. (Japanese Journal of Applied Physics, Vol. 22, No. 8, August, 1983 pp. 1332 to 1334) is an example of the former.